Add a step to the error tracking docs

Instruct users to create a Sentry projects for each gitlab project.

doc/user/project/operations/error_tracking.md

@@ -20,6 +20,7 @@ You will need at least Maintainer [permissions](../../permissions.md) to enable
 GitLab provides an easy way to connect Sentry to your project:
 
 1. Sign up to Sentry.io or [deploy your own](#deploying-sentry) Sentry instance.
+1. [Create](https://docs.sentry.io/guides/integrate-frontend/create-new-project/) a new Sentry project. For each GitLab project that you want to integrate, we recommend that you create a new Sentry project.
 1. [Find or generate](https://docs.sentry.io/api/auth/) a Sentry auth token for your Sentry project.
    Make sure to give the token at least the following scopes: `event:read` and `project:read`.
 1. Navigate to your project’s **Settings > Operations**.